Lasers emitting in the THz frequency range of 0.1 to 10 THz are known. For example, U.S. Pat. Nos. 7,471,449, 7,508,578, 7,706,056, 7,430,074, and 7,440,178 to Korenblit and Tankhilevich describe magnon lasers which emit in the THz frequency range. In such magnon lasers, lasing is predicted to occur in a lasing medium of ferromagnetic semiconductor material involving spin-up and spin-down electrons in a classic 4 level sub-band laser structure [A. E. Siegman, ‘Lasers’, University Science Books, 1986.]. The magnon lasing emission occurs for transitions between the upper two sub-band. Above a certain threshold, annihilating non-equilibrium magnons will lase and produce THz radiation, whose intensity depends on the magnon collision rate.
Lasing is achieved by a balance between various length scales, the mean free path of electrons in the medium, the spin-wave wavelength, the sample dimensions, and the radiated wavelength. To lase, the ambient temperature must be below a critical temperature, where recent results have shown that with the right materials, the critical temperature may be as high as 850° C. In a one hundred layer magnon laser incorporating semiconductor magnon mirrors, the CW (continuous wave) power can be increased 100-fold, and yet the device thickness may be less than 4 microns.
Korenblit and Tankhilevich's own predictions for their CW magnon laser are for a threshold current exceeding 5000 Amps/cm2, and employing 10-100 Watts of input electrical power, where it might be possible to extract ˜10 mW of laser power for a single-stage laser and ˜1 Watt for a 100 stage laser. The required threshold current and input electrical power for output laser power exceeds other known solid-stage lasers for this wavelength range, where wavelengths should be in the 0.2 to 2.0 THz region, with a laser line width of ˜1 MHz.
Moreover, currently most powerful THz emitters are relatively feeble. Cooled Quantum Cascade Lasers (QCL) lasers emit microWatts of power, with the best prospects being mW. The best research-level MMICs emit only 50 mW of power at 0.22 THz.